1. Field of the Invention
The present invention relates to a semiconductor device in which a parasitic capacitance can be prevented, and to an image scanning unit utilizing the same and an image forming apparatus utilizing the same.
2. Description of the Prior Art
It is generally well known that an adhesive material (sealing material) is used in a space between a semiconductor chip and a substrate to reduce a physical stress by a thermal expansion on a circuit in order to prevent an electrical breakage at contacting point in an electrical circuit which is caused by a difference between the coefficient of thermal expansions of them when a semiconductor chip is bonded on a substrate by means of a face down bonding technology.
In the past when a semiconductor chip is utilized as an optical device, in order to prevent an occurrence of problem that an electrical performance of the device can not be carried out because the adhesive materials for the semiconductor chip happens to inundate to the accepting surface (or the light emitting surface) of the device and block off the light path, a method is employed in that a protruding portion is arranged for the adhesive material not to wraparound the accepting surface as disclosed in Japanese Laid Open Patent Hei 06-204442.
However in the above described method, there were problems that a manufacturing cost of the device was got higher to form the protruding portion, and the production process for it was made complicated because there was a need that the protruding portion had to be made at the entire circumference of the semiconductor chip and the need had to be satisfied in the process.
The above described wraparound problem is viewed with suspicion not only in the optical devices but also in a device for high frequency circuit. In the high frequency circuit, there may be a fear that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance. It is very difficult to estimate the parasitic capacitance with preliminary survey especially when it is made in a large scale production, and it is impossible to make an amount of the wraparound constantly without fluctuation. In a recent movement of a realization of high speed driving of semiconductor, the problem of parasitic capacitance comes out to fore and it causes an unable problem to disregard in the whole business world of semiconductor mounting.
Because of these situation an object of the present invention is to provide a semiconductor device, an image scanning unit and an image forming apparatus in that there are no need to arrange the protruding portion and in that the parasitic capacitance is prevented.
To attain the above described object by the present invention a semiconductor device including: a substrate which has a wiring portion; and a semiconductor chip which has a functional surface in a front surface thereof and which is bonded by flip chip bonding onto the substrate; wherein an adhesive material which is used to adhere and fix the semiconductor chip and the substrate, adheres the substrate on at least one surface other than both of the front surface and an opposing surface thereof, and wherein the adhesive material does not enter into a space between the substrate and the semiconductor chip, is provided.
By this arrangement the adhesive material does not contact with a functional surface of the semiconductor chip and the above described problems are solved that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance and that adhesive material block off the light path because it wraparound the light accepting surface (or the light emitting surface). At the same time the semiconductor chip can give the heat generated in the semiconductor chip away to environment because the adhesive material does not cover an opposite surface of the semiconductor functional surface.
In the semiconductor device according to the present invention the adhesive material is covered with adhesive material which has been cured. By this arrangement the adhesive material is prevented to flow out (prevention of flowing out) thereby the adhesive material would not enter between the functional surface of the semiconductor chip and the substrate because of flowing out of the adhesive material And at the same time a layout of the adhesive material becomes easier because an initial structure of the adhesive material is maintained.
In the semiconductor device according to the present invention a cross section of the adhesive material is a circular. By this arrangement in addition to the above described action for prevention of flowing out, the adhesive material has enough strength against internal and external pressure even before it is hardened. Also the production is easily performed.
In the semiconductor device according to the present invention a cross section of the adhesive material is a polygonal. By this arrangement in addition to the above described action for prevention of flowing out, the adhesive strength can be made higher because an adhering area between the adhesive material and the semiconductor chip and the substrate can be took wider.
In the semiconductor device according to the present invention the adhesive material is held by an adhesive material holding means. In this arrangement in addition to the above described actions that the adhesive material is prevented to contact with the functional surface of semiconductor chip and so on, the adhesive material would not wraparound between the functional surface of semiconductor and the substrate because the flowing out of adhesive material can be prevented effectively even when the adhesive material with low viscosity is utilized. According to this fact the adhesive material with low viscosity can be used as the adhesive material.
In the semiconductor device according to the present invention the adhesive material holding means is made of a sponge like material. By this arrangement the adhesive material in the supporting body can be operated with a negative pressure and by this negative pressure the adhesive material can be supported in the body.
In the semiconductor device according to the present invention the adhesive material holding means is made of an aggregated body of fibers. By this arrangement the adhesive material holding member can hold the adhesive material by means of the aggregated body of fibers.
In the semiconductor device according to the present invention the adhesive material holding means has a light transparent property. By this arrangement a photo curing type adhesive material can be used because whole surface of the held adhesive material is irradiated by a hardening light through the adhesive material supporting body.
In the semiconductor device according to the present invention the adhesive material adheres the substrate at entire circumference of surfaces other than both of the front surface and the opposing surface. By this arrangement in addition to the above described actions the problem would not occur that performance of the device can not be carried out because the adhesive material is not disposed on a light incident area and the light path of the incident light to (or outgoing light from) the semiconductor device would not block off by the adhesive material.
In the semiconductor device according to the present invention the adhesive material is a photo curing type adhesive material. By this arrangement the semiconductor chip and the substrate can be adhered to fix without any discrepancy of holding position due to thermal expansion because a rise in temperature would not almost occur when the adhesive material is cured by a light. Also it does never happen that a residual stress influenced by a temperature change in the adhering process.
In the semiconductor device according to the present invention the adhesive material is a heat curing type adhesive material having a curing temperature which is lower than a temperature that breaks a junction between the substrate and the semiconductor device. By this arrangement the adhesive material can be cured by a heat by means of utilizing a heat curing type adhesive material even where the portion can not be irradiated by a light. Because the curing temperature for the heat curing type adhesive material is selected at a predetermined temperature that is lower than a temperature that breaks the conjunction of electrode such as solder or golden bump and so on which electrically connects the semiconductor chip with the wiring portion of the substrate, the substrate and the semiconductor chip can be connected and fixed with maintaining a reliability of the electrical conjunction without occurrence of breakage of the conjunction.
In the semiconductor device according to the present invention the substrate is made of a light transparent material, the semiconductor chip has an optical functional surface and a space is formed between the optical functional surface and the light transparent substrate as a light incident space. By this arrangement in addition to the above described actions the problem would not occur that the performance of the device can not be carried out because the adhesive material is not disposed on a light incident area and the light path of the incident light to (or the outgoing light from) the semiconductor device would not block off by the adhesive material.
By the present invention a semiconductor device including: a substrate which has a wiring portion in a front surface thereof; and a semiconductor chip which has a functional surface and which is bonded by flip chip bonding onto the substrate; wherein an adhesive material which is used to adhere and fix the semiconductor chip and the substrate, adheres the substrate on at least one surface other than both of the front surface and an opposing surface thereof, the adhesive material does not enter into a space between the substrate and the semiconductor chip, and wherein a heat radiating means is disposed at the back surface of the semiconductor chip, is provided.
By this arrangement the adhesive material does not contact with a functional surface of the semiconductor chip and the above described problems are solved that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance and that adhesive material block off the light path because it wraparound the light accepting surface (or the light emitting surface). At the same time the semiconductor chip can give the heat generated in the semiconductor chip away to environment and prevent a deformation of the semiconductor chip because the adhesive material does not cover an opposite surface of the semiconductor functional surface and the heat radiating means is disposed.
In the semiconductor device according to the present invention the heat radiating means is made of an elastic member which performs an elastic deformation according to a thermal deformation of the semiconductor chip along a direction of the functional surface of the semiconductor chip. By this arrangement the heat radiating means would not regulate against the expansion and the contraction by heat and thereby the expansion and the contraction of the heat radiating means does not effect on the semiconductor chip. By this arrangement the semiconductor chip and the substrate are made to be free from the thermal stress other than caused by themselves, and thereby they are free from deformation by an external force.
In the semiconductor device according to the present invention the elastic member is a wave like member which is formed in a wave like shape. By this arrangement the heat radiating means can have the elasticity along an expansion and a contraction direction of the semiconductor chip even when the heat radiating means are made of a hard material.
In the semiconductor device according to the present invention the elastic member is a spiral like member which is formed in a spiral shape. By this arrangement the heat radiating means can have the elasticity along an expansion and a contraction direction of the semiconductor chip even when the heat radiating means are made of a hard material.
In the semiconductor device according to the present invention the heat radiating means is a wire like member which is formed in a wire like shape. By this arrangement to the expansion or the contraction of the semiconductor chip which is caused by heat the heat radiating means would not regulate to the expansion and the contraction along the direction of the expansion and the contraction because the heat radiating means is made to have a smaller contacting area space contacting with the semiconductor device. And at the same time he heat radiating means would not give an influence the stress to the semiconductor chip caused by a deformation of itself.
In the semiconductor device according to the present invention the heat radiating means is a spike like member which is formed in a spike like shape. By this arrangement to the expansion or the contraction of the semiconductor chip which is caused by heat, the heat radiating means would not regulate to the expansion and the contraction along the direction of the expansion and the contraction because the heat radiating means is made to have a smaller contacting area space contacting with the semiconductor device. And at the same time he heat radiating means would not give an influence the stress to the semiconductor chip caused by a deformation of itself.
In the semiconductor device according to the present invention the heat radiating means is a spherical member which is formed in a spherical shape. By this arrangement to the expansion or the contraction of the semiconductor chip which is caused by heat, the heat radiating means would not regulate to the expansion and the contraction along the direction of the expansion and the contraction because the heat radiating means is made to have a smaller contacting area space contacting with the semiconductor device. And at the same time he heat radiating means would not give an influence the stress to the semiconductor chip caused by a deformation of itself.
In the semiconductor device according to the present invention the semiconductor chip is a solid state image forming device. By this arrangement in addition to the above described actions the problem would not occur that performance of the device can not be carried out because the adhesive material is not disposed on a light incident area and the light path of the incident light to (or outgoing light from) the semiconductor device would not block off by the adhesive material.
The present invention is characterized by an image scanning unit including the above described semiconductor device. By this arrangement because the incident light to the solid state image forming device is not blocked off and the performance of solid state image forming device can be carried out sufficiently, there is no possibility of occurrence of error in reading the image data and thereby the image scanning unit with high reliability can be provided.
Also the present invention is characterized by an image forming apparatus including the above described image forming unit. By this arrangement because the performance of solid state image forming device can be carried out sufficiently, there is no possibility of occurrence of error in reading the image data and because the image forming apparatus includes the image forming unit which can carry out the image forming with high reliability, the apparatus can form electrostatic latent image with high accuracy thereby there is no possibility of occurrence of error in reading the image of the manuscript.